Present day household refrigerators usually include in its lower portion an uninsulated space in which a compressor and/or a condenser are housed together with a drip pan. An example of such refrigerator is disclosed in Canadian Pat. No. 703,567 issued Feb. 9, 1965. A drain tube is usually provided to discharge melted frost water into the pan where it receives heat from the condenser and the motor compressor unit in an amount sufficient to cause evaporation of the water collected in the pan at rates sufficient to keep the pan from overflowing. In some cases, such as disclosed in U.S. Pat. No. 2,907,180 issued Oct. 6, 1959, there is provided in the machine compartment housing the condenser and the compressor, some means providing a water seal so that air will not be drawn up from the machine compartment through the discharge tube into the refrigerator.